Various electronic endoscopes wherein such solid state imaging device as a charge coupled device (CCD) is used as an imaging means are recently suggested.
It is preferable that the insertable part of an electronic endoscope using the above mentioned solid state imaging device is made as small as possible in the diameter. However, for that purpose, it is necessary that the solid state imaging apparatus to be embedded into the tip of the insertable part of the endoscope should be made small.
In a conventional solid state imaging apparatus, as disclosed in the patent gazette of Japanese patent laid open No. 163315/1986, a solid state imaging chip is provided parallelly with the surface of a base member and is arranged at right angles with the optical axis of an objective lens, such electronic parts as an amplifying circuit and a driving circuit for producing various driving clocks are fitted to another substrate different from the base member, the substrate is then connected to the back surface of the base member and the above mentioned electronic parts are enclosed on the periphery with an electric shielding member or the like so as to be packaged.
In the above mentioned solid state imaging apparatus, there are defects that it is necessary to electrically connect the base member on which the solid state imaging chip is arranged and the substrate on which the electronic parts are fitted with each other, a space is required in the connecting part and therefore the outside diameter of the package is large and that, in case the package of this solid state imaging apparatus is provided within the endoscope tip part, the outside diameter of the endoscope tip part will be large and the length of the rigid part of the endoscope tip part will be large. Further, as the connecting parts increase as between the solid state imaging chip and the base member and between the base member and substrate, more defective products will be produced in the producing step and the reliability itself will reduce.
Also, as disclosed in the specification of U.S. Pat. No. 4,573,450, a solid state imaging chip is provided parallelly with the surface side of a base member and is arranged parallelly with the optical axis of an objective so that the optical axis may be bent by using such optical part as a prism and led to the solid state imaging chip.
The above mentioned solid state imaging apparatus has defects that, as not only the size of the prism but also the thickness of the cover glass provided on the surface of the solid state imaging chip, the thickness of the solid state imaging chip itself and the thickness of the base member are in the diametral direction of the endoscope, the tip part of the endoscope will have to be thick.